scale-crop-image.swift

func scaleAndCropImage(_ image: UIImage, toSize newSize: CGSize) -> UIImage {
    if image.size.equalTo(newSize) {
        return image
    }
    
    // Find the ratios of the desired dimensions to the current dimensions,
    // and use the larger one to scale the image to fill the desired size
    let widthFactor = newSize.width / image.size.width
    let heightFactor = newSize.height / image.size.height
    let scaleFactor = max(widthFactor, heightFactor)
    
    let scaledSize = CGSize(width: image.size.width * scaleFactor, height: image.size.height * scaleFactor)
    
    // Inset the origin to draw from so that the intersection of the new size and scaled size will be centered
    let drawingOrigin = CGPoint(x: (newSize.width - scaledSize.width) / 2.0, y: (newSize.height - scaledSize.height) / 2.0)
    
    let drawingRect = CGRect(origin: drawingOrigin, size: scaledSize)
    
    // Passing an image context scale of 0.0 results in a scale equal to the screen's scale
    UIGraphicsBeginImageContextWithOptions(newSize, false, 0.0)
    image.draw(in: drawingRect)
    let scaledImage = UIGraphicsGetImageFromCurrentImageContext()!
    UIGraphicsEndImageContext()
    
    return scaledImage
}